1. Field of the Invention
The invention relates to a method and apparatus for effecting the noncontact opening of a flapper valve disposed downhole in a well by developing an intermediate pressure force which reduces the force needed to open the valve and minimizes the possibility of damage to the flapper valve when significant well pressures are maintaining it in a closed position.
2. Description of the Prior Art
Conventional packers used in subterranean wells often incorporate a spring-loaded flapper valve on the bottom of the packer just below the cylindrical seal bore of the packer. When a production tool or production tubing is pulled from the packer, the flapper valve is shifted to its closed position by the spring. Well fluid pressures below the packer thus act to increase the closing forces on the flapper valve so that the combination of the spring force and the fluid pressure forces amount to a substantial bias on the flapper valve maintaining it in its closed position.
When it is desired to reinsert a production tool or production tubing through the packer, it has been common to utilize an irregular mule shoe end on the inserted tool. It often happens that the lowermost point of the mule shoe end of the production tool contacts the flapper valve at a position very close to the hinge of the valve, hence at a position where little effective leverage is exerted on the flapper valve. When the flapper valve is retained in its closed position by a substantial well fluid pressure, the application of sufficient downward force to the mule shoe to effect the opening of the flapper valve will instead shear the pivot pin mounting of the flapper valve, hence resulting in significant damage, possibly forcing the shut down of the well to replace the packer and the broken flapper valve.
It is therefore desirable to effect the opening of a downhole flapper valve, at least to the extent of relieving fluid pressure across the valve, through the application of fluid pressure forces which unlike mechanical contact forces cannot act only adjacent the flapper hinge.